Antifuse programmable element using ferroelectric material

Abstract

An electrically programmable antifuse element using ferroelectric materials for the insulative dielectric layer, methods for producing same, and an integrated circuit applying a plurality of ferroelectric antifuse elements in a two dimensional matrix of rows and columns for use as a programmable logic device (PLD) or as a programmable read-only memory (PROM). A ferroelectric material is formed between two conductive electrodes to create a ferroelectric antifuse element. In an alternative embodiment, a plurality of chemically distinct materials is layered to form the dielectric layer. The combined application of an AC electric field and a DC electric field breaks down the ferroelectric material to form a low-resistance conductive filament. The synergy of the two electric fields permits programming antifuse elements of the present invention by applying DC electric fields as low as 2 volts amplitude. In the preferred embodiment, as compared to prior designs, antifuse devices of the present invention display higher resistivity in the unprogrammed state due to the high dielectric constant of ferroelectric materials and lower resistivity in the programmed state because the ferroelectric material breaks down into metal oxide conductive filaments. The resistivity of the conductive filament may be reduced further by the blending of materials through substitution rather than doping processes.

We claim: 
     
       1. An electrically programmable antifuse device comprising: first and second electrodes;   a dielectric layer electrically insulating said first electrode from said second electrode, said dielectric layer comprising a layered superlattice material; and   fusing means for controllably altering said dielectric layer to form an electrical conductor connecting said first and second electrodes.   
     
     
       2. The programmable antifuse device of claim 1 wherein said dielectric layer comprises strontium bismuth titanate (SrBi 2  Ta 2  O 9 ). 
     
     
       3. The programmable antifuse device of claim 1 wherein said dielectric layer comprises a plurality of layers of physically distinct materials. 
     
     
       4. The programmable antifuse device of claim 3 wherein said plurality of layers of physically distinct materials comprises a first layer of strontium bismuth titanate (SrBi 2  Ta 2  O 9 ) and a second layer of zinc oxide (ZnO). 
     
     
       5. The programmable antifuse device of claim 3 wherein said plurality of layers of physically distinct materials comprises a first layer of strontium bismuth titanate (SrBi 2  Ta 2  O 9 ) and a second layer of barium bismuth titanate (Ba x  Bi y  TiO 3 ). 
     
     
       6. The programmable antifuse device of claim 1 wherein said first electrode includes a barrier layer. 
     
     
       7. The programmable antifuse device of claim 1 wherein said second electrode includes a barrier layer. 
     
     
       8. The programmable antifuse device of claim 1 wherein said fusing means comprises: means for controllably applying an AC electric field of predetermined AC amplitude across said first and second electrodes; and means for controllably applying a DC electric field of predetermined DC amplitude across said first and second electrodes. 
     
     
       9. An electrically programmable antifuse device comprising: first and second electrodes;   a dielectric layer electrically insulating said first and second electrodes, said dielectric layer comprising a plurality of physically distinct materials selected to form a conductive material when fused, wherein at least one of said plurality of physically distinct materials is a layered superlattice material; and   fusing means for controllably altering said dielectric layer to form an electrical conductor connecting said first and second electrodes.   
     
     
       10. The programmable antifuse device of claim 9 wherein said plurality of physically distinct materials comprises a first layer of strontium bismuth titanate (SrBi 2  Ta 2  O 9 ) and a second layer of zinc oxide (ZnO). 
     
     
       11. The programmable antifuse device of claim 9 wherein said plurality of physically distinct materials comprises a first layer of strontium bismuth titanate (SrBi 2  Ta 2  O 9 ) and a second layer of barium bismuth titanate (Ba x  Bi y  TiO 3 ). 
     
     
       12. The programmable antifuse device of claim 9 wherein said first electrode includes a barrier layer. 
     
     
       13. The programmable antifuse device of claim 9 wherein said second electrode includes a barrier layer. 
     
     
       14. The programmable antifuse device of claim 9 wherein said fusing means further comprises: means for controllably applying an AC electric field of predetermined AC amplitude across said first and second electrodes; and means for controllably applying a DC electric field of predetermined DC amplitude across said first and second electrodes. 
     
     
       15. A programmable array integrated circuit comprising: a substrate material;   a plurality of row electrode means formed in substantially parallel rows on said substrate material;   a plurality of column electrode means formed in substantially parallel columns substantially perpendicular to said plurality of row electrode means, each of said plurality of column electrodes intersecting the plane of each of said plurality of row electrodes;   dielectric means for electrically insulating each of said intersecting row and column electrode means, said dielectric means comprising a layered superlattice material; and   fusing means for controllably altering said dielectric means at any one of said intersections of said row and column electrode means to form an electrical conductor connecting said one of said intersecting row and column electrode means.   
     
     
       16. The programmable array integrated circuit of claim 15 wherein said dielectric means comprises strontium bismuth titanate (SrBi 2  Ta 2  O 9 ). 
     
     
       17. The programmable array integrated circuit of claim 15 wherein said dielectric means comprises a plurality of layers of physically distinct materials, and wherein a low impedance electrically conductive material is formed to electrically connect said intersecting row and column electrode means by operation of said fusing means on said plurality of materials. 
     
     
       18. The programmable array integrated circuit of claim 17 wherein said plurality of layers of physically distinct materials comprises a first layer of strontium bismuth titanate (SrBi 2  Ta 2  O 9 ) and a second layer of zinc oxide (ZnO). 
     
     
       19. The programmable array integrated circuit of claim 17 wherein said plurality of layers of physically distinct materials comprises a first layer of strontium bismuth titanate (SrBi 2  Ta 2  O 9 ) and a second layer of barium bismuth titanate (Ba x  Bi y  TiO 3 ). 
     
     
       20. The programmable array integrated circuit of claim 15 wherein said row electrode means includes a barrier layer. 
     
     
       21. The programmable array integrated circuit of claim 15 wherein said column electrode means includes a barrier layer. 
     
     
       22. The programmable array integrated circuit of claim 15 wherein said fusing means further comprises: means for controllably applying an AC electric field of predetermined AC amplitude across said one of said intersecting row and column electrode means; and means for controllably applying a DC electric field of predetermined DC amplitude across said one of said intersecting row and column electrode means.